Configurable Pass-Through of SIP INVITE Parameters

The Configurable
Pass-Through of SIP INVITE Parameters feature enables the Cisco Unified Border
Element (Cisco UBE) platform to pass through end-to-end headers at a global or
dial peer level that are not processed or understood in a Session Initiation
Protocol (SIP) trunk to SIP trunk scenario. The pass-through functionality
includes all or only a configured list of unsupported or non-mandatory SIP
headers and all unsupported content or Multipurpose Internet Mail Extensions
(MIME) types.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see
Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for
Configurable Pass-Through of SIP INVITE Parameters

Configuring the
media
flow-around command is required for Session Description Protocol
(SDP) pass-through. When flow-around is not configured, the flow-through mode
of SDP pass-through will be functional.

When the
dial-peer media flow mode is asymmetrically configured, the default behavior is
to fall back to SDP pass-through with flow-through.

Cisco Unified Border Element

Cisco IOS
Release 15.0(1)M or a later release must be installed and running on your Cisco
Unified Border Element.

Cisco Unified Border Element
(Enterprise)

Cisco IOS XE
Release 3.1S or a later release must be installed and running on your Cisco ASR
1000 Series Router.

Restrictions for Configurable
Pass-Through of SIP INVITE Parameters

When Session
Description Protocol (SDP) pass-through is enabled, some of the interworking
that the Cisco Unified Border Element currently performs cannot be activated.
These features include:

Delayed Offer to
Early Offer Interworking

Supplementary
Services with Triggered Invites

Flow-around calls will not work with SDP pass through

DTMF Interworking
Scenarios

Fax
Interworking/QoS Negotiation

Transcoding

For configurable
pass-through of SIP INVITE parameters, the following features for Session
Initiation Protocol (SIP)-SIP dial-peer rotary calls are not supported:

With CSCty41575,
the unsupported header and content pass-through functionalities mentioned above
are addressed.

Information About
Configurable Pass-Through of SIP INVITE Parameters

Cisco Unified Border
Element (Cisco UBE) does not support end-to-end media negotiation between the
two endpoints that establish a call session. This is a limitation when the
endpoints intend to negotiate codec or payload types that Cisco UBE does not
process because, currently, unsupported payload types are not negotiated by
Cisco UBE. Unsupported content types include text or plain, image or jpeg and
application or resource-lists and XML. To address this problem, Session
Description Protocol (SDP) is configured to pass transparently through Cisco
UBE so that both the remote ends can negotiate media independent of Cisco UBE.

Session Description
Protocol (SDP) pass-through is addressed in two modes:

Flow-through—Cisco UBE plays no role in the media negotiation. It terminates
and reoriginates the Real-time Transport Protocol (RTP) packets irrespective of
the content type negotiated by both endpoints. Flow-through supports address
hiding and Network Address Translation (NAT) traversal.

Flow-around—Cisco
UBE neither plays a part in media negotiation nor does it terminate and
reoriginate media. Media negotiation and media exchange is completely
end-to-end.

Non-mandatory
Headers

You can configure
Cisco UBE to pass through headers that are not mandatory (headers that Cisco
UBE does not pass through by default). You can configure a list of headers to
be passed across. The list can contain any header except the mandatory headers
shown in the table below.

Technical
Assistance

Description

Link

The
Cisco Support website provides extensive online resources, including
documentation and tools for troubleshooting and resolving technical issues with
Cisco products and technologies.

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receive security and technical information about your products, you can
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Access
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password.

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

This feature
extends the Pass-Through List functionality to specify the pass-through of
unsupported headers as well. The following command was introduced:passthru-hdr-unsupp
.

Configurable
Route-String Header Pass-Through using a Pass Through List

Cisco IOS XE Release 3.10S

This
feature enables the Cisco UBE to pass through end-to-end headers that are not
processed or understood in a SIP trunk to SIP trunk scenario by specifying the
headers to be passed through in a pass through list. The pass through
functionality will includes only the configured list of non-mandatory SIP
headers.

The
following commands were introduced or modified:
passthru-hdr,
voice class
sip-hdr-passthrulist.

Configurable Pass-Through of SIP INVITE Parameters

Cisco IOS XE Release 3.1S

This
feature enables the Cisco UBE to pass through end-to-end headers that are not
processed or understood in a SIP trunk to SIP trunk scenario. The pass through
functionality includes all or only a configured list of unsupported or
non-mandatory SIP headers, and all unsupported content/MIME types.

The
following commands were introduced or modified:
pass-thru and
voice-classsippass-thru.